The technical field of the present invention is that of heat exchangers and, more particularly, of plate-based tubes with flow disturbers which equip them. These exchangers are used especially as an evaporator in an air-conditioning system in an automobile or as a radiator in the cooling circuit of such a vehicle.
Heat exchangers, called plate exchangers, in the shape of an I or a U, generally consist of the assembly of several flat tubes juxtaposed with each other and connected together by a separator, the aim of which is to promote heat exchange. Each of these tubes is formed by the face-to-face assembly of two plates which thus define a circulation duct into which the fluid flows. This fluid may be a refrigerant in the case of an evaporator or a coolant in the case of a radiator.
It is known from the prior art to place flow disturbers in the fluid circulation duct. These flow disturbers are very often an integral part of the plates forming the tube. The aim of these flow disturbers is to create turbulence on passage of the fluid so as, on the one hand, to increase the heat exchange between the fluid and the plates and, on the other hand, to provide mechanical integrity of the tube bundle of the exchanger.
One of the main drawbacks of this configuration is the creation of acoustic noise due to overspeed of the fluid, noise which it is increasingly important to overcome, given the increasing level of comfort demanded within a vehicle.
Another drawback of this type of assembly lies in the fact that it does not offer very good circulation performance or optimum efficiency given the virtually uncontrolled arrangement of the flow disturbers in the prior art.
The aim of the present invention is therefore to solve the drawbacks described above mainly by placing the flow disturbers on the plates so as to maintain a substantially constant passage cross section for the fluid in the circuit while keeping the advantages associated with the turbulence created by the latter. This therefore involves optimizing both aspects of decreasing pressure drops and of promoting heat exchange.
The subject of the invention is therefore a tube for a heat exchanger through which a fluid flows, intended to promote heat exchange between an external medium and said fluid, formed by at least two plates connected to each other in order to define a circulation duct, the cross section of which is a cross section for passage of said fluid, said circulation duct having a fluid inlet orifice and a fluid outlet orifice, wherein said tube comprises a means for partially blocking the circulation duct intended to keep the passage cross section of said duct substantially constant between the inlet orifice and the outlet orifice.
According to one characteristic of the invention, the tube has the general shape of a xe2x80x9cUxe2x80x9d comprising a base connected to two arms, said arms being separated by a rib, the end of which is terminated by a junction, the passage cross section to be kept constant being any one of those which lie between the rib and a peripheral edge of the U-shaped tube and passing through the partial blocking means.
According to another characteristic of the invention, the shape of the junction is circular with a diameter greater than twice the width of the rib.
According to yet another characteristic of the invention, the peripheral edge has connection regions connecting the two arms at the base of the U-shaped tube, said regions being of circular shape and of a radius enabling the passage cross section to be kept constant.
Advantageously, the partial blocking means is defined by the positioning of flow disturbers each with respect to the others such that their cumulated blocking cross sections are substantially constant over the entire length of the circulation duct.
The passage cross section is constant when the difference between a minimum passage cross section and a maximum passage cross section determined in the circulation duct does not exceed 20 percent. This blocking means is also defined by the shape of the flow disturbers each with respect to the others in the circulation duct.
Advantageously again, the flow disturbers are placed on at least one of the plates.
Similarly, the flow disturbers are placed on at least one of the plates such that the direction of the axis supporting their largest dimensions is substantially parallel to the circulation direction of the fluid.
According to one variant of the invention, the flow disturbers are present on both plates.
According to another variant of the invention, at least one flow disturber of one of the plates is placed facing at least one flow disturber of the other plate.
The flow disturbers of each plate are placed facing each other, the directions of their axes supporting their largest dimensions being substantially parallel to each other.
According to one characteristic of the invention, the plates are securely attached by the flow disturbers.
According to another characteristic of the invention, the flow disturbers have an oval shape or a circular shape.
According to yet another characteristic of the invention, the flow disturbers have the shape of a diamond, advantageously with rounded angles.
The flow disturbers have a pyramid shape, the base of the pyramid shape being common with one of the plates. Advantageously, a heat exchanger comprises at least one tube defined according to any one of the preceding characteristics.
The heat exchanger is a radiator or an evaporator.
A very first advantage of the device according to the invention lies in the reduction of sound noise of this type of exchanger.
Another advantage lies in the optimization of the combination of efficiency together with the sound noise.
Another advantage of the invention lies in the possibility of optimizing the internal pressure drop in the tube.
Another advantage is the improvement of the combination of the efficiency characteristics together with the mechanical integrity.